This invention relates generally to an electrostatographic printer or copier, and more particularly concerns a cleaning apparatus used therein.
In an electrophotographic application such as xerography, a charge retentive surface (i.e. photoconductor, photoreceptor or imaging surface) is electrostatically charged, and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being produced. The toner image may then be transferred to a substrate (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is well known, and useful for light lens copying from an original, and printing applications from electronically generated or stored originals, where a charge surface may be imagewise discharged in a variety of ways. Ion projection devices where a charge is imagewise deposited on a charge retentive substrate operate similarly.
Although a preponderance of the toner forming the image is transferred to the paper during transfer, some toner invariably remains on the charge retentive surface, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, Kaolin and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimum operation that the toner remaining on the surface be cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed on automatic xerographic devices utilizes a rotatable brush that frictionally engages the imaging surface to remove the residual toner and paper particles therefrom.
In brush cleaners such as those in a xerographic cleaner where a rotating brush is used to clean (via mechanical, electrostatic, or other means) toner (or other particles such as carrier beads, paper fibers, etc.) from the photoreceptor (or any other surface for that matter), detoning (or cleaning) the brush is necessary. Air detoning is one method where an air stream is pulled through the brush fibers, carrying away toner (and other collected debris). To enhance the lessening of debris from the brush fibers in this type of system, flicking devices (one or more) are employed to disturb the fibers and a nearby air slot provides the air flow to pull away loosened debris. The mechanical flicking is accomplished by placing some type of "flicker", e.g. a round bar, in the path of the rotating fibers. The location of "flicker bar" relative to an air slot, i.e. upstream and/or downstream may have different effects on the overall detoning performance, but will depend on the specific application. Typically, the flicker bar is considered a high wear item and requires replacement at specified intervals.
Various problems exist with the present cleaner brush detoning systems. In some systems, a flicker bar may be positioned on one side of an air passage with the other side formed by a separate part, leading to assembly-to-assembly variations in the air passage size and negatively affecting air flow characteristics that can result in clogging of the air passage. When the air passage is clogged, additional servicing (beyond servicing of the flicker bar) is required to clear the air passage. Normally, the flicker bar can only be accessed after some degree of disassembly which results in high service costs.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 3,706,108 to Taylor discloses removing residual toner particles from a photoconductive surface using a rotating brush that contacts the surface. Removal of the residual toner particles from the brush fibers is assisted by applying a bias voltage to the brush to attract the toner particles to the brush and by using a flicker bar to loosen the toner particles from the cleaning blades.
U.S. Pat. No. 4,123,154 to Fisher discloses a cleaning apparatus wherein a flicker element removes residual material from a cleaner element. The flicker element works together with a corona charging device to neutralize the charge on the toner to aid in removal of the toner from the cleaning element.
U.S. Pat. No. 4,435,073 to Miller shows a cleaning brush with a plurality of flicker bars, at least one of which is fabricated from a material that will cause the charge on the brush to reverse at least once for every revolution of the brush, such reversal taking place while the brush fibers are subject to a toner removing airflow.